A network game has been played by two or more players in a common virtual space with game machines connected with a network. In order to actualize the network game, an environment for unifying results of processes between the machines which participate in the network game is necessary since the network game is played between the machines that physically separate from each other.
When playing the network game, a server periodically synchronizes with the respective game machines so that timing of the processes is unified in a common game progress between the respective game machines. By doing so, generation of discrepancy on the game progress, such as time series lag in a common game progress to be executed between the respective game machines, is avoided (see Japanese patent application publication No. 2008-99906).
The network game is actualized by using a common virtual space and locating two or more player characters to be operated by two or more players in such a space. For example, the player starts the game after locating one's own player character in the virtual space that is also used for the players in the other game machines. The player can play the network game with the other player if the player character of the other player participates in the common virtual space prepared in advance. (see Japanese patent application publication No. 2002-248273).
Documents to be disclosed for the invention are Japanese patent application publication No. 2008-99906 (paragraph 0008) and Japanese patent application publication No. 2002-248273 (paragraphs 0031 and 0032).